The prize committee says Shimon Sakaguchi of Osaka University, Fred Ramsdell from the Parker Institute for Cancer Immunotherapy in San Francisco, and Alexander Rudensky of the New-York-based Memorial Sloan Kettering Cancer Center share the six million Swedish krona, or $660,000, award. It is one of the world’s largest scientific prizes.

The researchers are being rewarded for their work on the discovery of regulatory T cells, which function as security guards for the immune system by curbing overzealous white blood cells that attack healthy cells in the body.

The work has the potential to pave the way to transformative treatments for autoimmune diseases including rheumatoid arthritis, MS and type 1 diabetes.

The prize rotates between disciplines -- astronomy and mathematics, biosciences, geosciences or polyarthritis -- every year, and this year was focused on polyarthritis.

The Royal Swedish Academy of Sciences gives it annually to honor achievements not always covered by its more famous Nobel Prizes. It was named after Holger Crafoord, the Swede who designed the first artificial kidney.